A magnetoresistance effect element is an element which changes its electric resistance when an external magnetic field is applied to it. A well-known one of the magnetoresistance effect elements is a TMR (Tunnel Magneto Resistance) element (also referred to as a “MTJ (Magnetic Tunnel Junction) element”) configured to store information and detect magnetism using a TMR effect. Recent years, there has been an increasing expectation that the MTJ element will be used for a MRAM (Magnetoresistive Random Access Memory) and the like.
Non Patent Document 1 discloses a perpendicular magnetization MTJ element. The perpendicular magnetization MTJ element includes a structure in which a free layer (magnetization free layer), a tunnel barrier layer and a reference layer (magnetization fixed layer) are stacked one on another. The direction in which to magnetize the free layer and the reference layer is parallel to the direction in which to stack the free layer and the reference layer.
An increase in an MR ratio (magnetoresistance ratio) is important for the purpose of enhancing characteristics of the MRAM device using the TMR element. A layered structure including CoFeB/MgO/CoFeB which is described in Patent Document 1 is known for its high MR ratio greater than 100%.
FIG. 10 shows an example of an MTJ element using a technique described in Non Patent Document 1. The MTJ element 1000 shown in FIG. 10 is a perpendicular magnetization MTJ element (p-MTJ element) with a bottom pin structure. The MTJ element 1000 has a bottom electrode 1002, and a Ta layer (seed layer) 1003 on a substrate 1001. On top of the Ta layer 1003, the MTJ element 1000 has a Co/Pt laminate 1004, a Co layer 1005, a Ru layer 1006, a Co layer 1007, a Pt layer 1008, a Co/Pt laminate 1009 and a Ta layer (spacer layer) 1010. Furthermore, on top of the Ta layer 1010, the MTJ element 1000 has a CoFeB layer 1011 as a reference layer, a MgO layer (barrier layer) 1012, a CoFeB layer 1013 as a free layer (magnetization free layer), a capping layer 1014, and a top electrode 1015. The Co/Pt laminate 1004 of the MTJ element 1000 is a laminate obtained by alternately stacking Co layers and Pt layers in a predetermined number of repeats (N times). In addition, the laminate 1009 of the MTJ element 1000 is a laminate obtained by alternately stacking Co layers and Pt layers in a predetermined number of repeats (M times).
FIG. 11 shows an example of a perpendicular magnetization MTJ element (p-MTJ element) using a technique described in Patent Document 1. The MTJ element 2000 shown in FIG. 11 has a laminate 2005 including Co layers and Ni layers instead of the Co/Pt laminate 1004 of the MTJ element 1000. Furthermore, the MTJ element 2000 has a Ni layer 2009 instead of the Pt layer 1008, and a laminate 2010 including Co layers and Ni layers instead of the Co/Pt laminate 1009.